I have a pilotless furnace . My board has 2 lights 1 red 1 yellow . My furnace is running once after I turn the gas v off for 5 minutes . But won't come on again when needed . My yellow is flashing continuously indicating false flame relay short , where is my flame sencor ?

[email protected]

Please post brand and model of your furnace. Flame Sensor is located near burners. When the thermostat calls for heat what is happening?